The use of light emitting diodes (LEDs) which are installed in headlights or luminaries that include a projection of the light via optical elements such as lenses or reflectors, or which are installed in sensors and have to be aligned highly accurately with a receiver, requires an alignment of the LEDs according to optical standpoints. While at present surface-mounted components, which also include the majority of LEDs, are aligned exclusively according to their geometrical center in order to place them positionally accurately, more and more nowadays there are applications in which the LEDs have to be aligned primarily according to the midpoint of their light emitting luminous area or of the incorporated LED chip.
In practice, however, there is typically an (undesired) offset between the geometrical center of an LED component, said geometrical center being determined in practice on the basis of the spatial position of the connection contacts such as connection areas or connection pins, and the light emitting luminous area. Such an offset can be between 0 and 100 μm (100×10−6).
In order that, however, rather than the geometrical center the midpoint of the light emitting area of a light emitting diode (LED) is accurately aligned with an optical axis of an optical arrangement or of an optoelectronic light receiving component, it is therefore necessary, in the course of an LED component being mounted on a component carrier, to measure the light emitting luminous area using an optical system and then to position and fix the LED component on the component carrier such that the midpoint of the light emitting luminous area of the relevant LED rather than the geometrical center of the LED component is located accurately on the placement position specified in a placement program of an automatic placement machine.
In order to approximately determine the spatial offset between the light emitting luminous area and the geometrical center of an LED component, it is known for the LED component to be measured either as early as in a feed unit used to feed the LED component to an automatic placement machine, or at a specific location within the automatic placement machine. The LED component is then collected by means of a pick-up tool, for example a suction pipette, such that the pick-up tool lands on the previously measured midpoint of the light emitting luminous area. The LED component is then placed onto a component carrier without a further position correction to a predefined desired position. What is problematic about this procedure is that a position correction can no longer be carried out for the LED component, which position correction would be necessary if the LED component is rotated somewhat or slips for example in the course of temporary placement, since then the previously performed position measurement of the light emitting luminous area is more or less useless. Moreover, in the extreme case, the offset between the luminous area and the electrical connection contacts could be so great that the LED component can no longer be soldered with the necessary quality in the case of a placement based on an ideal alignment according to the midpoint of the luminous area. In such a case, a placement with the relevant LED component should logically be prevented. However, this is not possible owing to the lack of information concerning the offset between the light emitting luminous area and the electrical connection contacts. Consequently, this results in a relatively low process reliability when populating component carriers with LED components.